Not to add confusion to the discussion I believe one factor in PRRs paint color has been overlooked. As will be noted from the attached, paint was mixed on site from bulk quantities of pigment powders, linseed oil, and japan. Of the ingredients the pigment though specified by PRR standards, could be different from lot to lot and manufacturer to manufacturer.
This is the closest info I could find. Though years back I ran across a page from PRRs standards book, while searching out their engine shops,on mixing their engine colors. I recall reading that the shop foreman was responsible with verifying the pigment tone by mixing a set amount to see what color was achieved. Pigment that did not meet his approval was returned.
Though the info presented here specifies freight car mix, the same applied to their engine color. Pigment was added by the lb not run through a computer. Variations would occur so, though close, each batch was possibly different in finished tone. We see and hear an assortment of formulas to achieve Brunswick Green when in reality it’s still just a green hued black that we associate with the Pennsy.
http://steamerafreightcars.com/prototype/frtcars/prr-carcolor.pdf